[Ada] AI-162

[Arnaud Charlet <charlet at adacore dot com>]

Tested on i686-linux, committed on trunk

On going work for Ada 2005 AI-162
AI-162 specifies that anonymous objects created for access parameters
in a call have a short lifetime, namely the innermost full statement
or expression that encloses the call. This rule leads to the creation
of transient blocks in additional places, to finalize these objects
earlier. Previously such objects were finalized at the end of the
innermost enclosing master context (block, subprogram, task body, etc).

In addition, the use of 'Address with class-wide interface objects requires a
call to the run-time subprogram that returns the base address of
the object. After this patch the execution of gnat.dg/interface1.adb
raises no exception.

Finally, an incomplete type can be tagged, and an access parameter
of the type is a legal controlling argument of a primitive operation of
the type. However, a dispatching call to this primitive operation is
illegal before the completion of the type, because the call freezes the
designated type of the formal.
In Ada 2005 mode, the following package must be rejected with the message:
--
stt.ads:6:22: premature use of incomplete type "T" in dispatching call
--
package Stt is
   type T is tagged;
   function F return access T'Class;
   function G (X : access T) return Integer;
   I : Integer := G (F);
   type T is tagged null record;
end Stt;

2007-04-06  Geert Bosch  <bosch@adacore.com>
	    Ed Schonberg  <schonberg@adacore.com>
	    Javier Miranda  <miranda@adacore.com>
	    Bob Duff  <duff@adacore.com>

	* exp_ch4.adb (Expand_N_Type_Conversion): Remove special processing
	for conversion of a Float_Type'Truncation to integer.

	* exp_attr.adb (Is_Inline_Floating_Point_Attribute): New function to
	check if a node is an attribute that can be handled directly by the
	back end.
	(Expand_N_Attribute_Reference): Suppress expansion of floating-point
	attributes that can be handled directly by the back end.
	(Expand_N_Attribute_Reference, case 'Access and 'Unchecked_Access):
	use new predicate Is_Access_Protected_Subprogram_Type.
	(Expand_N_Attribute_Reference, case 'Write): The reference is legal for
	and Unchecked_Union if it is generated as part of the default  Output
	procedure for a type with default discriminants.
	(Expand_N_Attribute_Reference): Avoid the expansion of dispatching calls
	if we are compiling under restriction No_Dispatching_Calls.
	(Constrained): Use Underlying_Type, in case the type is private without
	discriminants, but the full type has discriminants.
	(Expand_N_Attribute_Reference): Replace call to Get_Access_Level by
	call to Build_Get_Access_Level.
	(Expand_N_Attribute_Reference): The use of 'Address with class-wide
	interface objects requires a call to the run-time subprogram that
	returns the base address of the object.
	(Valid_Conversion): Improve error message on illegal attempt to store
	an anonymous access to subprogram value into a record component.

	* sem_res.adb (Resolve_Equality_Op): Detect ambiguity for "X'Access =
	null".
	(Simplify_Type_Conversion): New procedure that performs simplification
	of Int_Type (Float_Type'Truncation (X)).
	(Resolve_Type_Conversion): Call above procedure after resolving operand
	and before performing checks. This replaces the existing ineffective
	code in Exp_Ch4.
	(Set_String_Literal_Subtype): When creating the internal static lower
	bound subtype for a string literal, use a newly created copy of the
	subtree representing the lower bound.
	(Resolve_Call): Exclude build-in-place function calls from transient
	scope treatment. Update comments to describe this exception.
	(Resolve_Equality_Op): In case of dispatching call check violation of
	restriction No_Dispatching_Calls.
	(Resolve_Call): If the call returns an array, the context imposes the
	component type of the array, and the function has one non-defaulted
	parameter, rewrite the call as the indexing of a call with a single
	parameter, to handle an Ada 2005 syntactic ambiguity for calls written
	in prefix form.
	(Resolve_Actuals): If an actual is an allocator for an access parameter,
	the master of the created object is the innermost enclosing statement.
	(Remove_Conversions): For a binary operator, check if type of second
	formal is numeric, to check if an abstract interpretation is present
	in the case of exponentiation as well.

Attachment: difs
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